Method of making cellulosic materials with oxidizing power



United States Patent 3,304,147 METHQD OF MAKING CELLULOSIC MATERIALS WITH OXKDIZENG POWER Robert M. Reinhardt, New Orleans, Russell M. H. Kullman, Metairie, and John G. Frick, Jr., New Orleans, La., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed June 24, 1963, Ser. No. 290,262 16 Claims. (Cl. 8116.3)

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to the treatment of cellulosic materials. The object of this invention is to prepare cellulosic materials such as fabric, yarn, rope, linters, or bat-ting that have oxidizing power and that contain positive or available chlorine, but do not suffer autodegradation in storage or use.

It is known that the treatment of cellulosic textiles, to which an amide-formaldehye condensate has been applied, with inorganic hypochlorites results in the formation of chloramides on the textile. The retained chlorine in this form is positive chlorine, and has oxidizing power. Cellulosic textiles containing this chlorine, however, lose strength on storage, particularly at elevated temperatures. The strength loss is due apparently to the formation of acids from the retained chlorine. For this reason the retention of positive chlorine is generally considered disadvantageous, and rarely is use made of the oxidizing power of the textile with retained chlorine.

The object of this invention can be attained by chemically modifying the cellulosic textile or other material so that it contains chemically bound carboxyl groups. The textile is then treated with an amide-formaldehyde condensate and the bound carboxyl groups converted to the salt'form with alkali metal cations before treatment with hypochlorite. After treatment with hypochlorite the textile retains oxidizing chlorine, and is less susceptible to strength loss on standing or use, even at elevated temperatures.

Chemical modification of the cellulosic material for the purpose of this invention can be accomplished by oxidation of the cellulose, whereby a portion of the cellulosic hydroxyl groups is converted to carboxyl groups, or preferably by etherification of a portion of the cellulosic hydroxyl groups with groups containing a carboxyl substituent. An example of the latter process is the etherification of cellulose with chloroacetic acid to form a partially carboxymethylated cellulose, as described in US. Patent 2,448,153. Other etherifying groups that may be used include carboxyethyl, carboxymethyl, and carboxymethylene groups. For this invention, modifications giving about 0.03 to 0.15 carboxyl groups for each anhydroglucose unit of the cellulose are suitable.

The amide-foramldehyde condensates useful in this invention are those that are commonly used in finishing cellulosic textiles for special properties, such as wrinkle resistance, and that are not specifically designed to avoid chlorine retention. Typical examples are N-methylol carboxylic amides, dimethylol urea, and methylol ureas of lower substitution. These may be applied to the modified cellulosic materials in the same manner as they are applied to unmodified cellulosic textiles. Such an application typically consists in the treatment of the cellulosic material with an aqueous solution of the amide formaldehyde condensate followed by drying a heat treatment.

The acidic catalysts used in the treatment of unmodified cellulosic textiles, however, can be omitted in many cases with the modified cellulosic material containing carboxyl groups.

An application to give 0.1 to 3.0% nitrogen content on the modified cellulose is satisfactory for the purpose of this invention. The higher nitrogen contents give increased chlorine content after hypochlorite treatment and consequently higher oxidizing capability.

Conversion of the carboxyl group to the salt form after treatment with the amide-formaldehyde condensate is accomplished by washing the treated materials with solutions made mildly alkaline by the addition of alkali metal bases, such as sodium hydroxide, sodium carbonate, potassium carbonate, or mixtures of these. A wash of pH 8 to pH 11 is suitable for this purpose. Introduction of positive chlorine is accomplished most economically by treatment with aqueous solutions of alkali metal hypochlorites, such as the sodium hypochlorite commonly used for bleaching textiles. It may be accomplished, however, by the use of organic hypochlorites or chloramines. In most cases conversion of the carboxyl group to the salt, and introduction of positive chlorine can be accomplished in a single step.

The reduced tendency to lose strength in the chlorinecontaining cellulosic textiles of this invention is apparently due to the protective action of the alkali metal salt against the acids formed by the chlorine. The fact that such salts are chemically part of the cellulose and not merely deposited on or within it, therefore, is advantageous. The textile so modified can be retreated after the chlorine originally introduced is reduced by use or by prolonged storage without loss of the protective agent by leaching in the retreatment.

The products of this invention are useful for the oxidation of materials in solution whereby the residue of reduced oxidizing agent, in the form of a textile product or loose insoluble material can be removed readily to minimize contamination of the solution. They are also useful for the making of protective clothing whereby a wearer can be protected from injurious materials that can be rendered innocuous by oxidation.

The following examples illustrate the invention in greater detail.

EXAMPLE 1 Cotton print cloth was carboxymethylated by the process of US. Patent 2,448,153 to a D8. of 0.07 (an average of 0.07 carboxymethyl group for each anhydroglucose unit of the cellulose).

Swatches of this fabric were treated with urea-formaldehyde precondensate which had been prepared by the reaction of 1.75 moles of formaldehyde with 1 mole of urea at pH 8 for 16 hours. The carboxymethylated cotton was padded to about wet pickup of a solution containing 7.5% urea-formaldehyde and 2.8% of 2-amino-2-rnethyl-l-propanol hydrochloride as catalyst, mounted on pin frames, dried at 60 C. for seven minutes, cured at 160 C. for three minutes, afterwashed with an alkaline solution of a nonionic detergent, and dried. Nitrogen content of the washed fabric was 1.31%; breaking strength was 41.4 lbs. (American Society for Testing Materials, test method D39-59.)

A sample of the carboxymethylated fabric after treatment with the urea-formaldehyde was chlorinated with a solution of sodium hypochlorite containing 0.25% available chlorine at a pH of 9.5, thoroughly rinsed, and air-dried. Analysis of the fabric by titration of the iodine released from acidified potassium iodide showed that it contained 0.48% available chlorine and had an oxidizing capacity of meq./kg. The fabric had a breakiing strength of 36.2 lbs. after chlorination and scorching by Tentative Test Method 92-1958T of the American Association of Textile Chemists and Colorists.

3 That is, the chlorinated fabric retained 87% of its original strength after the standard scorch test for damage caused by retained chlorine.

EXAMPLE 2 A sample of unmodified cotton print cloth was treated with urea-formaldehyde precondensate as in Example 1. The fabric contained 1.27% nitrogen, and had a breaking strength of 35.0 lbs. When chlorinated as in Example 1, the fabric contained 0.60% available chlorine but retained only 14% of its original strength after the standard scorch test for damage caused by retained chlorine.

EXAMPLE 3 Results obtained on samples of c'arboxymethylated (D.S. 0.07) and unmodified cotton treated with ureaformaldehyde and then chlorinated with sodium hypochlorite solution are compared in the following table. Two concentrations of urea-formaldehyde and three different catalys'ts were employed. Also, carboxymethylated cotton was treated with urea-formaldehyde without added catalyst.

In all instances the carboxymethylated cotton showed less tendency to lose strength in the scorch test, and in most instances had more oxidizing power than the unmodified cottons with similar treatments.

Cotton fabrics were etherified by the following procedures to produce modified cotton fabrics containing carboxyl groups.

(a) A Z-carboxyethylated cotton with D.S. of 0.08 was obtained by treatment of cotton fabric with acrylonitrile and alkali followed by hydrolysisof the cyanoethylated cotton.

(b) A l-carboxyethylated cotton with a D.S. of 0.03 was obtained by treatment of cotton fabric with 1- chloropropionic acid and alkali.

(c) A carboxymethylenated cotton of D.S. 0.13 was obtained by treatment of cotton fabric with dichloro- Treatment with Unmodified Cotton Carboxymethylated Cotton After Chlorination Alter Chlorination N UF, percent Catalyst percent Scorch percent Scorch Avail. Cl, Ox. Cap., Test, Avail. Cl, Ox. Cap., Test,

percent meq./kg. percent percent meq./kg. percent Str. Ret. Str. Ret.

28% AH 1 1. 27 0.60 169 14 1. 31 0. 48 135 87 5.6% AH 1 3. 02 0.67 189 28 2. 84 1. 27 358 73 0.36% Zn (Na)2 1. 19 O. 44 124 24 1. 41 0. 58 163 88 0 72% ZI1(NO3)2 2. 71 0 41 115 55 2. 75 0.85 239 78 Na2CO 1. 14 0. 53 149 11 1. 02 0.85 239 75 None 1. 53 1. 43 403 58 l Z-amino-2-methyl1-propanol hydrochloride.

EXAMPLE 4 A sample of carboxymethylated cotton (D.S. 0.07) was padded with a urea-formaldehyde precondensate solution containing 0.72% zinc nitrate catalyst,

to about 80% wet pickup, was then mounted on a pin frame, dried at 60 C. for seven minutes, cured at 160 C. for three minutes, after-washed with an alkaline solution of nonionic detergent, and dried. The fabric was chlorinated by treatment with sodium hypochlorite solution, and had an available chlorine content of 1.30%. 55

EXAMPLE 5 A sample of carboxymethylated cotton (D.S. 0.07)

was treated with urea-formaldehyde precondensate using zinc nitrate catalyst as in Example 4, chlorinated with sodium hypochlorite solution, washed, and air-dried.

Below are shown results obtained upon treatment of various oxidizable solutions with swatches of this oXidizing fabric.

(a) Acidified potassium iodide s0luti0n.-When the oxidizing fabric was dipped into this solution the colorless potassium iodide solution turned yellow-red, indieating oxidation o iodide ion to iodine by the fabric.

The rechlorinated fabric had an oxidizing capaci- 60 acetic acid and alkali, as described in U.S. Patent 3,017,- 237.

(d) A 2-carboxyethyl'ated cotton of D.S. 0.10 was obtained by treatment of cotton fabric with acrylamide and alkali followed by hydrolysis of the carbamoylethylated cotton.

This series of modified cotton fabrics with an unmodified cotton fabric for comparison, were treated with an 18.8% solution of a urea-formaldehyde condensate with zinc nitrate catalyst. Preparation and application of the condensate were performed as described in Example 1. The fabrics were then treated with a hypochlorite solution, also as described in Example 1. Test results on the treated fabric are shown in the following table.

Each of the modified fabrics retained more chlorine and consequently had greater oxidizing power than the unmodified fabric. In adidtion the strength retention relative to the amount of retained chlorine is greater with the modified fabrics.

EXAMPLE 7 A sample of carboxymethylated cotton of D5. 0.07 was impregnated with a solution containing 20% of a condensate of formamide with two molar equivalents of formaldehyde and 4% magensium chloride hexahydrate. The fabric was dried, and then heat cured three minutes at 160 C. The fabric was washed once in an alkaline solution, soaked in a solution of sodium hypochlorite, and dried. A similar treatment was given to a cotton fabric that was not carboxylated.

Test results given in the following table show that the carboxymethylated fabric after treatment not only resisted damage from the retained chlorine but also had greater oxidizing power than the unmodified fabric.

Fabric Available Chlorine, Strength Retained in 1. A process for preparing a chemically modified cellulosic textile that exhibits oxidizing power and resists autodegradation comprising:

(a) etherifying the cellulose hydroxyl groups with a radical containing a carboxylic acid substituent and selected from the group consisting of carboxymethyl, 1 carboxyethyl, 2 carboxyethyl, and carboxymethylene to a degree of substitution of about from 0.03 to 0.15 of said radical per anhydroglucose unit of the cellulose;

(b) resin-treating the resulting etherified cellulosic textile with an amide-formaldehyde condensate which retains chlorine when treated with a chlorinating agent, by impregnating the etherified cellulosic textile with an aqueous solution containing a sufiicient quantity of the amide-formaldehyde condensate to give a 0.1% to 3.0% nitrogen content on the etherified cellulosic textile, followed by heating the impregnated cellulosic textile to dry and cure it;

(c) converting the carboxylic acid substituents of the resin-treated, etherified cellulosic textile to the alkali metal salt form by washing the textile with an alkaline solution containing an alkali metal base; and

(d) treating the resulting cellulosic textile with a chlorinating agent selected from the group consisting of an alkali metal hypochlorite, an organic hypochlorite, and a chloramine which introduces positive chlorine into the amide-formaldehyde condensate.

2. The process of claim 1 wherein the etherifying radical is carboxymethyl.

3. The process of claim 1 wherein the etherifying radical is l-carboxyethyl.

4. The process of claim 1 wherein the etherifying radical is 2-carboxyethyl.

5. The process of claim 1 wherein the etherifying radical is carboxymethylene.

6. The process of claim 1 wherein the amide-formaldehyde condensate is a urea-formaldehyde condensate.

7. The process of claim 1 wherein the resin-treating of the etherified cellulosic textile is carried out in the presence of an acidic catalyst.

8. The process of claim 1 wherein the chlorinating agent is an alkali metal hypochlorite.

9. A process for preparing a chemically modified eellulosic textile that exhibits oxidizing power and resists autodegradation comprising:

(a) etherifying the cellulose hydroxyl groups with a radical containing a carboxylic acid substituent and selected from the group consisting of carboxymethyl, 1 carboxyethyl, 2 carboxyethyl, and carboxymethylene to a degree of substitution of about from 0.03 to 0.15 of said radical per anhydroglucose unit of the cellulose;

(b) resin-treating the resulting etherified cellulosic textile by impregnating it with an aqueous solution containing a quantity of an amide-formaldehyde condensate, which retains chloride when treated with a chlorinating agent, sufficient to give a 0.1% to 3.0% nitrogen content in the etherified cellulosic textile,'followed by heating the impregnated cellulosic textile to dry and cure it; and

(c) treating the resintreated, etherified cellulosic textile with an alkaline solution containing an alkali metal hypochlorite which thereby converts the carboxylic acid substituents of the resin-treated, etherified cellulosic textile to the alkali metal salt form and introduces positive chlorine into the amideformaldehyde condensate.

10. The process of claim 9 wherein the etherifying radical is carboxymethyl.

11. The process of claim 9 wherein the etherifying radical is l-carboxyethyl.

12. The process of claim 9 wherein the etherifying radical is 2-carboxyethyl.

13. The process of claim 9 wherein etherifying radical is carboxymethylene.

14. The process of claim 9 wherein the amide-formaldehyde condensate is a urea-formaldehyde condensate.

15. The process of claim 9 wherein the resin-treating of the etherified cellulosic textile is carried out in the presence of an acidic catalyst.

16. The process of claim 9 wherein the alkali metal hypochlorite is sodium hypochlorite.

References Cited by the Examiner UNITED STATES PATENTS 2,584,114 2/1952 Daul et al 117-1394 2,824,779 2/1958 Reeves et al. 8-129 X 3,017,237 1/1962 Bullock et al. 8-120 3,041,199 6/1962 Miller et al. 3,069,409 12/1962 Henry et al.

OTHER REFERENCES Daul et al., Textile Research Journal, December 1952, pages 729-796.

Prick et al., Textile Research Journal, April 1957, pages 294-299.

Reinhardt et al., American Dye Reporter, July 28, 1958, pages 505-508.

Reid et al., Textile Industries, November 1958, pages 2-10.

Reinhardt et al., Textile Research Journal, October 1959, pages 802-810.

NORMAN G. TORCHIN, Primary Examiner.

H. WOLMAN, Assistant Examiner. 

1. A PROCESS FOR PREPARING A CHEMICALLY MODIFIED CELLULOSIC TEXTILE THAT EXHIBITS OXIDIZING POWER AND RESISTS AUTODEGRADATION COMPRISING: (A) ETHERIFYING THE CELLULOSE HYDROXYL GROUPS WITH A RADICAL CONTAINING A CARBOXYLIC ACID SUBSTITUENT AND SELECTED FROM THE GROUP CONSISTING OF CARBOXYMETHYL, 1 - CARBOXYETHYL, 2 - CARBOXYETHYL, AND CARBOXYMETHYLENE TO A DEGREE OF SUBSTITUTION OF ABOUT FROM 0.03 TO 0.15 OF SAID RADICAL PER ANHYDROGLUCOSE UNIT OF THE CELLULOSE; (B) RESIN-TREATING THE RESULTING ETHERIFIED CELLULOSIC TEXTILE WITH AN AMIDE-FORMALDEHYDE CONDENSATE WHICH RETAINS CHLORINE WHEN TREATED WITH A CHLORINATING AGENT, BY IMPREGNATING THE ETHERIFIED CELLULOSIC TEXTILE WITH AN AQUEOUS SOLUTION CONTAINING A SUFFICIENT QUANTITY OF THE AMIDE-FORMALDEHYDE CONDENSATE TO GIVE A 0.1% TO 3.0% NITROGEN CONTENT ON THE ETHERIFIED CELLULOSIC TEXTILE, FOLLOWED BY HEATING THE IMPREGNATED CELLULOSIC TEXTILE TO DRY AND CURE IT; (C) CONVERTING THE CARBOXYLIC ACID SUBSTITUENTS OF THE RESIN-TREATED, ETHERIFIED CELLULOSIC TEXTILE TO THE ALKALI METAL SALT FORM BY WASHING THE TEXTILE WITH AN ALKALINE SOLUTION CONTAINING AN ALKALI METAL BASE; AND (D) TREATING THE RESULTING CELLULOSIC TEXTILE WITH A CHLORINATING AGENT SELECTED FROM THE GROUP CONSISTING OF AN ALKALI METAL HYPOCHLORITE, AN ORGANIC HYPOCHLORITE, AND A CHLORAMINE WHICH INTRODUCES POSITIVE CHLORINE INTO THE AMIDE-FORMALDEHYDE CONDENSATE.
 9. A PROCESS FOR PREPARING A CHEMICALLY MODIFIED CELLULOSIC TEXTILE THAT EXHIBITS OXIDIZING POWER AND RESISTS AUTODEGRADATION COMPRISING: (A) ETHERIFYING THE CELLULOSE HYDROXYL GROUPS WITH A RADICAL CONTAINING A CARBOXYLIC ACID SUBSTITUENT AND SELECTED FROM THE GROUP CONSISTING OF CARBOXYMETHYL, 1 - CARBOXYEHTYL, 2 - CARBOXYEHTYL, AND CAROXYMETHYLENE TO A DEGREE OF SUBSTITUTION OF ABOUT FROM 0.03 TO 0.15 OF SAID RADICAL PER ANHYDROGLUCOSE UNIT OF THE CELLULOSE; (B) RESIN-TREATING THE RESULTING ETHERIFIED CELLULOSIC TEXTILE BY IMPRENATING IT WITH AN AQUEOUS SOLUTION CONTAINING A QUANTITY OF AN AMIDE-FORMALDEHYDE CONDENSATE, WHICH RETAINS CHLORIDE WHEN TREATED WITH A CHLORINATING AGENT, SUFFICIENT TO GIVE A 0.1% TO 3.0% NITROGEN CONTENT IN THE ETHERIFIED CELLULOSIC TEXTILE, FOLLOWED BY HEATING THE IMPREGNATED CELLULOSIC TEXTILE TO DRY AND CURE IT; AND (C) TREATING THE RESIN-TREATED, ETHERIFIED CELLULOSIC TEXTILE WITH AN ALKALINE SOLUTION CONTAINING AN ALKALI METAL HYPOCHLORITE WHICH THEREBY CONVERTS THE CARBOXYLIC ACID SUBSTITUENTS OF THE RESIN-TREATED, ETHERIFIED CELLULOSIC TEXTILE TO THE ALKALI METAL SALT FROM AND INTRODUCES POSITIVE CHLORINE INTO THE AMIDFORMALDEHYDE CONDENSATE. 